And we begin this hour with politics. It's day two of the Democratic National Convention in Charlotte, North Carolina. Tonight's headliner is former President Bill Clinton. And we have our own headliner, NPR's Mara Liasson, who's joining us from Charlotte with a look ahead. Hey, Mara.

MARA LIASSON, BYLINE: Hi, Melissa.

BLOCK: And there is some news today. President Obama will no longer be accepting his party's nomination tomorrow in the vast football stadium there in Charlotte. The organizers are saying the weather forced the event indoors.

LIASSON: Well, that's what they say, and there are going to be a lot of disappointed people who had tickets to that. Of course the Republicans immediately pounced and said the reason they're canceling it is because they couldn't fill the stadium, and they are pointing to weather reports that say it'll be just fine tomorrow night.

The fact is there has been a lot of rain, really torrential downpours here. They didn't want to risk having to evacuate the stadium in the middle of the event. And the Obama campaign said they had already given out 65,000 tickets, with 19,000 on a waiting list. The stadium holds about 73,000, and they say that they're going to try to give every one of those ticket holders entry to another event with the president between now and Election Day.

BLOCK: And do you see this having any kind of impact on the campaign?

LIASSON: Well, they miss out on the optics of a big stadium, cheering him on, and they miss out on some of the organizing benefits. Giving these volunteers a ticket was a real motivation and reward for their work. But still, there'll be plenty of enthusiasm inside, in the smaller venue in the arena here.

For a supposedly unenthusiastic party, these Democrats are pretty fired up not just to beat Mitt Romney, but for President Obama. And I thought the speakers last night on the first night of the convention really lit into Romney with a level of gusto that was certainly coordinated, but higher than I was expecting. It also shows the benefits of having the last word, of being able to go after the other guy's had his convention.

BLOCK: Well, let's talk about the speakers who'll be trying to fire up the crowd there tonight. One of them is Elizabeth Warren. She's in a tough race, running for the U.S. Senate in Massachusetts. She led the effort to create the Consumer Financial Protection Bureau. What do you see her role as being tonight?

LIASSON: Well, she's an absolute hero to the left-wing base of the Democratic Party. But she's struggling in Massachusetts, and that really maddens and mystifies Democrats. This is Ted Kennedy's seat in a year when President Obama is going to be on the top of the ballot.

So, tonight, she has to do herself some good, do the president some good, without reminding liberals why they're disappointed in the president on some issues. But I think that she will be really popular.

And she is the one, by the way, who initially formulated the you didn't build that line that's been ripped out of context by the Republicans. So she is an articulate defender of why the public sphere is important and it's an important foundation for prosperity.

BLOCK: And as we mentioned, Mara, the star of the show tonight is Bill Clinton. We talked about this on the program earlier this week. He and President Obama have a fraught relationship. It was, though, an invitation directly from President Obama to President Clinton to make the speech tonight and officially, I gather, put his name into nomination.

LIASSON: Right. It's the first time a former president has put a sitting president's name in nomination. President Clinton is incredibly popular. His favorable ratings have never been higher. He presided over a period of peace and prosperity. His implied message will be stick with Obama. We can do that again.

The Republicans, of course, are trying to use him as a foil. Newt Gingrich said today, oh, Clinton was a great president. Obama is pathetically bad in comparison. Of course he didn't think that about Bill Clinton at the time.

(LAUGHTER)

LIASSON: But he - but the Obama campaign feels that Clinton can tell the Obama story better than anyone, including Obama, and he can lay out the Democratic agenda in a way that's understandable. He can take the fight to Mitt Romney without looking mean.

Of course there's a risk. Not only there's the risk of making the president pale by comparison or look smaller, but also sometimes Bill Clinton goes off message. Not long ago, he said that Mitt Romney had a sterling business career. And the other day, we asked the Obama high command, who's vetting Bill Clinton's speech? And they said, Bill Clinton.

So you can't really control him, but there has been the famous rivalry between the two men, which is now patched up. Back in 2008, of course, he called President Obama, then-candidate Obama, a fairy tale. But the bottom line is the campaign feels he's a huge asset; otherwise, they wouldn't be using him in campaign advertising.

BLOCK: OK. Mara, thanks so much.

LIASSON: Thank you, Melissa.

BLOCK: That's NPR national political correspondent Mara Liasson at the Democratic National Convention in Charlotte. Transcript provided by NPR, Copyright National Public Radio.